UNIVERSITY    OF   CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL   EXPERIMENT  STATION 

CIRCULAR  No.  259 

April,   1923 

PEAR  BY-PRODUCTS 

By  J.  H.  IRISH 


The  latest  government  reports  show  that  a  crop  of  about  five 
hundred  thousand  tons  of  pears  is  produced  in  the  United  States 
annually.  Of  this  amount,  the  part  produced  in  California  is  about 
one  hundred  and  forty  thousand  tons.  The  marketing  of  this  fruit 
already  presents  a  difficult  problem,  although  only  one-half  of  the 
plantings  of  pear  orchards  in  this  state  have  come  into  bearing.  Any 
new  outlet  for  pears  is,  therefore,  worthy  of  consideration. 

Disposal  of  Pears  of  Better  Quality. — First  class  fruit  is  shipped 
east  as  fresh  fruit  from  some  localities  and  that  from  other  localities 
is  canned.  In  Lake  County,  which  produces  pears  of  remarkably  fine 
quality  and  where  the  transportation  facilities  are  poor,  practically 
all  of  the  pears  are  dried. 

Disposal  of  Culls. — In  the  Sacramento  Valley  the  cull  pears  amount 
to  about  three  thousand  tons  annually.  The  total  for  the  state  is 
estimated  by  the  Pear  Growers'  Association  at  fifteen  thousand  tons. 
At  present,  cull  pears  are  dried  and  yield  a  product  of  very  poor 
quality  or  they  are  sent  to  the  refuse  heap.  We  may  expect  that  the 
production  of  pears  in  the  state  will  have  doubled  within  the  next  five 
years.  To  be  profitable  this  increase  in  production  will  require  a 
great  expansion  of  the  market  or  a  limitation  of  shipments  by  very 
close  grading  which  will  allow  fruit  of  only  the  finest  quality  to  reach 
the  market.  It  must  be  accompanied  by  improvements  in  cultural 
methods,  which  will  produce  fruit  of  better  quality  and  eliminate 
culls,  or  by  finding  new  outlets  for  the  great  increase  of  culls. 

The  purpose  of  the  investigations  reported  in  this  publication  is  to 
discover  new  outlets  for  these  culls  in  the  form  of  pear  by-products. 

Culls  consist  of  malformed,  insect  injured,  sunburned,  or  otherwise 
blemished  fruit  which  can  neither  be  shipped  as  fresh  fruit  nor  canned. 
Culls  infested  with  Codling  Moth  are  of  little  value  for  by-products 
because  of  the  great  cost  of  trimming  out  affected  portions  of  the  fruit. 


2  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

PEAR  SPREAD 

Experiment  Work. — A  product  which  has  proved  very  satis- 
factory and  which  has  possibilities  of  becoming  of  commercial  value 
is  "Pear  Spread."  It  is  called  "Pear  Spread"  in  preference  to 
"Pear  Butter,"  because  its  quality  is  superior  to  that  of  the  old- 
fashioned  fruit  butters. 

The  method  recommended  for  making  this  product  was  developed 
in  the  Fruit  Products  Laboratory  by  blending  small  quantities  of 
pear  pulp  with  various  combinations  of  spices  and  varying  propor- 
tions of  sugar.  The  concentration  was  varied  by  cooking  for  varying 
times.  The  samples  were  tested  by  members  of  the  Fruit  Products 
class,  members  of  the  staff  and  visitors.  Samples  made  by  the  process 
and  formula  given  below  met  with  general  approval. 

During  the  season  of  1921  about  one-half  ton  of  pears,  furnished 
by  Mr.  F.  T.  Swett  of  the  Pear  Growers'  Association,  was  made  into 
this  product.  Part  was  used  for  experimental  purposes  in  determin- 
ing the  heat  penetration,  processing  temperature,  keeping  qualities, 
and  other  factors  of  the  process.  The  remainder  was  sold  in  Berkeley. 
During  the  1922  season  two  and  one-half  tons  of  cull  pears  was 
obtained  from  the  Pear  Growers '  Association  at  a  moderate  cost.  This 
was  made  into  ' '  Pear  Spread ' '  according  to  the  process  which  follows. 

Process. —  (a)  Preparation  of  Fruit.  The  fruit  is  washed,  and 
stems,  decayed  spots,  dirt  and  worm  traces  removed.  It  is  then  run 
through  an  apple  grater  and  placed  in  the  kettle.  For  the  experiment 
lot  a  steam  jacketed  kettle  was  used.  Direct  flame  and  other  types 
of  kettle  may  be  used  if  proper  precautions  are  taken  to  prevent 
scorching.  If  the  fruit  is  green,  about  one  gallon  of  water  is  added 
to  each  five-gallon  lot  of  pulp.  Thoroughly  ripe  pears  require  no 
water.  When  no  water  is  added  less  cooking  is  necessary  in  the  final 
concentration. 

When  the  pulp  is  soft  it  is  removed  from  the  kettle  and  run 
through  a  cyclone  tomato  pulper,  using  the  coarse  screen.  This 
removes  the  seeds,  hard  tissues  surrounding  them,  stems,  other  large 
hard  pieces,  and  a  few  of  the  larger  stone  cells.  Passing  it  through 
this  screen  a  second  time  removes  some  of  the  stone  cells  which  were 
forced  through  during  the  first  operation. 

When  all  the  pulp  has  been  screened  twice,  the  coarse  screen  is 
replaced  by  a  finishing  screen.  Passing  through  this  fine  screen  twice 
removes  most  of  the  stone  cells  and  makes  the  pulp  smooth. 

(b)  Cooking.  This  smooth  pulp  is  returned  to  the  double  jacketed 
steam  kettle  for  final  cooking.  The  amounts  given  in  the  following 
formula  are  suitable  for  a  ten-gallon  kettle. 


Circular  259]  PEAR  by-products  3 

Formula 

Ingredient  Amount  used 

Pear  pulp 6  gallons 

Cane  sugar  24  pounds 

Lemon  juice 1  quart 

Ground  cinnamon %  ounce 

Ground  cloves %  ounce 

Ground  ginger  '%  ounce 

Ground  nutmeg  %  ounce 

First  the  sugar  is  added  to  the  pulp  in  the  kettle  and  stirred  until 
entirely  dissolved.  This  mixture  is  boiled,  with  continual  stirring, 
until  the  desired  consistency  is  reached,  which  is  at  about  221°  F. 
Lemon  juice  is  then  added  and  boiling  continued  until  the  desired 
consistency  is  again  reached  at  221°  F.  It  is  then  removed  from  the 
fire  and  spices  added,  and  stirring  continued  until  the  spices  have 
been  thoroughly  mixed.  This  condition  is  reached  when  no  lumps 
appear  in  the  product  and  when  it  presents  a  smooth,  creamy  appear- 
ance. It  is  placed  in  cans  and  sealed  while  hot.  If  sealed  before  the 
temperature  drops  below  185°  F.,  no  further  processing  is  necessary. 
(c)  Sterilizing.  If  allowed  to  cool  before  filling  the  cans,  steriliza- 
tion is  necessary.  Number  2  cans  require  boiling  in  water  one  and  one- 
half  hours  at  212°  F.,  for  safety.  Experiments  show  that  at  least 
seventy  minutes'  heating  in  boiling  water  is  necessary  to  heat  the 
center  of  a  Number  2  can  of  "spread"  to  a  temperature  of  175°  F., 
from  an  initial  temperature  of  60°  F. 

The  following  containers  have  been  found  satisfactory : 

Number  2  tin  can,  net  contents  24  ounces. 

Number  1  tall  tin  can,  net  contents  20  ounces. 

Jam  can,  net  contents  8  ounces. 

Vacuum  sealed  jelly  glass,  net  contents  4  ounces. 

Vacuum  sealed  jelly  glass,  net  contents  6  ounces. 

PEAE  VINEGAB* 

Cull  fresh  pears  yielded  a  very  good  vinegar  of  four  and  one-half 
per  cent  acetic  acid  content.  The  fruit  was  crushed  and  pressed  and 
the  juice  fermented  with  a  selected  cider  yeast.  After  the  completion 
of  the  yeast  fermentation,  a  starter  of  strong  cider  vinegar,  about 
twenty  per  cent  by  .volume,  was  added,  and  the  barrel  containing  the 
liquid  left  at  room  temperature  for  the  completion  of  the  vinegar 
fermentation.     This  required  about  three  months.     Natural  fermen- 


*  The  experiments  on  pear  vinegar  and  syrup  were  made  by  W.  V.  Cruess 
and  those  on  pear  candies  by  J.  B.  Vance. 


4  UNIVERSITY  OF  CALIFORNIA EXPERIMENT  STATION 

tation  of  pear  juice  gave  a  weak  vinegar  of  poor  flavor  and  appear- 
ance. The  use  of  selected  yeast,  therefore,  appears  to  be  necessary. 
It  was  found  possible  by  fermenting  the  crushed,  unpressed  pears 
with  selected  yeast  before  pressing  to  greatly  increase  the  yield  of 
juice  and  to  facilitate  the  pressing  operation.  A  ton  of  cull  pears 
will  yield  about  one  hundred  and  forty  to  one  hundred  and  fifty 
gallons  of  finished  vinegar. 

Specific  directions  for  the  manufacture  of  vinegar  may  be  found 
in  Bulletin  Number  287,  sent  free  on  application  to  the  College  of 
Agriculture,  Berkeley. 

PEAR  CANDY 

Pear  spread,  combined  with  apple  pectin  and  boiled  to  224°  F., 
makes  a  pleasing  candy  center.  This  may  be  coated  with  fondant,  or 
chocolate,  or  both. 

Sun-dried  and  dehydrated  pears  of  high  quality  were  dipped  in 
chocolate  and  were  found  to  give  very  satisfactory  candies  suitable 
for  "five  cent  sellers."  The  process  used  was  as  follows:  Soft,  pliable 
dried  pears  were  used.  Dipping  chocolate,  known  as  the  dark  amber 
grade,  was  melted  in  a  pan  placed  in  water  at  85-95°  F.  (not  above 
95°  F.).  The  pears  were  dipped  in  this  melted  chocolate  and  spread 
on  wax  paper  to  permit  hardening  of  the  chocolate. 

It  is  believed  that  this  product  has  commercial  possibilities. 

PEAE  SYEUP 

Pears  were  crushed,  pressed,  and  the  juice  thus  obtained  was  boiled 
and  filtered.  It  was  concentrated  in  an  open  jelly  kettle,  yielding  a 
syrup  of  dark  amber  color  and  pleasing  baked  pear  flavor.  The 
addition  of  sugar  before  concentration  at  the  rate  of  about  three 
pounds  to  the  gallon  of  juice  increased  the  yield  without  impairing 
the  quality.  Without  the  addition  of  sugar  about  twenty  to  twenty- 
five  gallons  of  syrup  to  the  ton  of  fruit  is  obtainable.  The  syrup 
should  be  suitable  for  table  use  and  cooking. 

EQUIPMENT 

Most  canneries  and  jelly  factories  possess  the  necessary  equipment 
for  preparing  pear  spread  and  pear  syrup.  Pear  candies  can  be  made 
in  any  candy  factory  or  in  the  home  kitchen  without  special  equip- 
ment. Existing  cider  vinegar  factories  could  use  cull  pears  for 
vinegar  without  interfering  with  the  crushing  of  apples,  since  these 
ripen  later  than  pears. 


